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Vol. 220. Issue 7.
Pages 458 (October 2020)
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Reply to: Ivermectin in COVID-19. Argumentum ad ignorantiam?
Réplica: Ivermectina en COVID-19. ¿Argumentum ad ignorantiam?
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M.L. López Reboiro, C. Sardiña González, J. López Castro
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jlcastro126@hotmail.com

Corresponding author.
Servicio de Medicina Interna, Hospital Público de Monforte, Lugo, Spain
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Dear Director,

After closely reading the letter by Carlosama-Rosero in which we were cited,1 we observed some misinterpretations of the content of our publication2 and we believe it would be useful to provide some clarifications.

In our previous letter, we reference the mental process known as argumentum ad ignorantium, which consists of believing that lack of awareness of evidence contrary to an idea that we support counts as evidence in its favor. At that time, we gave the example of the drug ivermectin in COVID-19 disease, whose previous success in a laboratory study would be difficult to extrapolate to clinical practice, as it would require toxic doses to reach the necessary therapeutic concentration.2

Although it is well-known that ivermectin dosing is in µg/kg of body weight, we gave the total necessary dosage in mg for reaching a concentration in human beings that is similar to what was effective in vitro, which would indeed be highly toxic (1000–1200 mg vs 10–20 mg, which is the dose habitually used in humans). At no point did we intend to categorically rule out ivermectin as a possible treatment for COVID-19, but rather refute inconsistent evidence in its favor. The work by Rajter et al.3 that Carlosama-Rosero cites is a multicenter retrospective study of 280 patients treated with ivermectin which reported a significant reduction in the overall mortality rate in the group that received ivermectin (15% vs 25.2%; OR 0.52 [CI 95% 0.29–0.96], p = 0.03). Furthermore, on the regression analysis adjusted for confounding variables, the reduction in mortality remained significant (OR 0.27 [CI 95% 0.09–0.85], p = 0.03; HR 0.37 [CI 95% 0.19–0.71], p = 0.03). However, like all observational studies, it had some well-known selection and confounding biases, and therefore the results reported in that publication must be taken with great caution and of course after waiting for the results of ongoing clinical trials. This work unfortunately does not allow for drawing solid conclusions on the effectiveness of ivermectin at this time.

References
[1]
Y. Carlosama-Rosero.
Ivermectina en COVID-19. ¿Argumentum ad ignorantiam?.
[2]
M. López Reboiro, C. Sardiña González, J. López Castro.
COVID-19 y Argumentum ad ignorantiam o «no todo vale».
[3]
JC Rajter, M Sherman, N Fatteh, F Vogel, J Sacks, J-J Rajter.
ICON (Ivermectin in COvid Nineteen) study: use of Ivermectin is asssociated with lower mortality in hospitalized patientes with COVID 19.
MedRxiv, (2020),

Please cite this article as: López Reboiro M.L. Sardiña González C. Réplica: Ivermectina en COVID-19. ¿Argumentum ad ignorantiam? Rev Clin Esp. 2020;220:458.

Copyright © 2020. Elsevier España, S.L.U. and Sociedad Española de Medicina Interna (SEMI)
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